The present invention relates generally to methods and apparatus for providing percutaneous access to the human sacral and lumbar vertebrae in alignment with a visualized, trans-sacral axial instrumentation/fusion (TASIF) line in a minimally invasive, low trauma, manner.
It has been estimated that 70% of adults have had a significant episode of back pain or chronic back pain emanating from a region of the spinal column or backbone. Many people suffering chronic back pain or an injury requiring immediate intervention resort to surgical intervention to alleviate their pain.
The spinal column or back bone encloses the spinal cord and consists of 33 vertebrae superimposed upon one another in a series which provides a flexible supporting column for the trunk and head. The vertebrae cephalad (i.e., toward the head or superior) to the sacral vertebrae are separated by fibrocartilaginous intervertebral discs and are united by articular capsules and by ligaments. The uppermost seven vertebrae are referred to as the cervical vertebrae, and the next lower twelve vertebrae are referred to as the thoracic, or dorsal, vertebrae. The next lower succeeding five vertebrae below the thoracic vertebrae are referred to as the lumbar vertebrae and are designated L1-L5 in descending order. The next lower succeeding five vertebrae below the lumbar vertebrae are referred to as the sacral vertebrae and are numbered S1-S5 in descending order. The final four vertebrae below the sacral vertebrae are referred to as the coccygeal vertebrae. In adults, the five sacral vertebrae fuse to form a single bone referred to as the sacrum, and the four rudimentary coccyx vertebrae fuse to form another bone called the coccyx or commonly the xe2x80x9ctail bonexe2x80x9d. The number of vertebrae is sometimes increased by an additional vertebra in one region, and sometimes one may be absent in another region.
Typical lumbar, thoracic and cervical vertebrae consist of a ventral or vertebral body and a dorsal or neural arch. In the thoracic region, the ventral body bears two costal pits for reception of the head of a rib on each side. The arch which encloses the vertebral foramen is formed of two pedicles and two lamina. A pedicle is the bony process which projects backward or anteriorly from the body of a vertebra connecting with the lamina on each side. The pedicle forms the root of the vertebral arch. The vertebral arch bears seven processes: a dorsal spinous process, two lateral transverse processes, and four articular processes (two superior and two inferior). A deep concavity, inferior vertebral notch, on the inferior border of the arch provides a passageway or spinal canal for the delicate spinal cord and nerves. The successive vertebral foramina surround the spinal cord. Articulating processes of the vertebrae extend posteriorly of the spinal canal.
The bodies of successive lumbar, thoracic and cervical vertebrae articulate with one another and are separated by intervertebral discs formed of fibrous cartilage enclosing a central mass, the nucleus pulposus that provides for cushioning and dampening of compressive forces to the spinal column. The intervertebral discs are anterior to the vertebral canal. The inferior articular processes articulate with the superior articular processes of the next succeeding vertebra in the caudal (i.e., toward the feet or inferior) direction. Several ligaments (supraspinous, interspinous, anterior and posterior longitudinal, and the ligamenta flava) hold the vertebrae in position yet permit a limited degree of movement.
The relatively large vertebral bodies located in the anterior portion of the spine and the intervertebral discs provide the majority of the weight bearing support of the vertebral column. Each vertebral body has relatively strong bone comprising the outside surface of the body and weak bone comprising the center of the vertebral body.
Various types of spinal column disorders are known and include scoliosis (abnormal lateral curvature of the spine), kyphosis (abnormal forward curvature of the spine, usually in the thoracic spine), excess lordosis (abnormal backward curvature of the spine, usually in the lumbar spine), spondylolisthesis (forward displacement of one vertebra over another, usually in the lumbar or cervical spine) and other disorders, such as ruptured or slipped discs, degenerative disc disease, fractured vertebra, and the like. Patients who suffer from such conditions usually experience extreme and debilitating pain and often neurologic deficit in nerve function.
Approximately 95% of spinal surgery involves the lower lumbar vertebrae designated as the fourth lumbar vertebra (xe2x80x9cL4xe2x80x9d), the fifth lumbar vertebra (xe2x80x9cL5xe2x80x9d), and the first sacral vertebra (xe2x80x9cS1xe2x80x9d). Persistent low back pain is attributed primarily to degeneration of the disc connecting L5 and S1. There are two possible mechanisms whereby intervertebral disc lesions can instigate and propagate low back pain. The first theory proposes that the intervertebral disc itself produces pain through trauma or degeneration and becomes the primary source of low back pain. Proponents of this theory advocate removal of the painful disc to relieve the low back pain.
Two extensive procedures are available to remove the disc and fuse the adjacent vertebrae together. One method is to replace the disc with bone plugs by going through the spinal canal on either side of the central nerve bundle. This method requires extensive stripping of the paraspinal musculature. More importantly, there are extensive surgical manipulations within the spinal canal itself. Although the initial proponents of this approach report 90% excellent to good results, subsequent studies have been unable to obtain acceptable outcomes and recommend adding internal fixation to improve fusion rates.
The second procedure is the anterior lumbar fusion which avoids the morbidity of posterior muscle stripping by approaching the spine through the abdomen. Surgeons experienced with this technique also report good to excellent patient results in 90% of cases performed. However, when generally used by practicing surgeons, the procedure was found to have a high failure rate of fusion. Attempts to increase the fusion rate by performing a posterior stabilization procedure have been successful, but the second incision increases the morbidity and decreases the advantages of the technique. Thus, the present surgical techniques available to remove and fuse painful lumbar discs are extensive operative procedures with potentially significant complications.
The other proposed mechanism for the intervertebral disc to cause low back pain concerns its affect on associated supportive tissues. The theory states that disc narrowing leads to stress on all of the intervertebral structures. These include the vertebral bodies, ligamentous supports, and facet joints. Surgeries designed to fuse and stabilize the intervertebral segment can be performed through the posterior approach. This is the original surgical procedure which was used to treat low back pain, and it also entails extensive muscular stripping and bone preparation.
There is no single procedure which is universally accepted to surgically manage low back pain patients. Although damaged discs and vertebral bodies can be identified with sophisticated diagnostic imaging, the surgical procedures are so extensive that clinical outcomes are not consistently satisfactory. Furthermore, patients undergoing presently available fusion surgery experience uncomfortable, prolonged convalescence.
A number of devices and techniques involving implantation of spinal implants to reinforce or replace removed discs and/or anterior portions of vertebral bodies and which mechanically immobilize areas of the spine assisting in the eventual fusion of the treated adjacent vertebrae have also been employed or proposed over the years In order to overcome the disadvantages of purely surgical techniques. Such techniques have been used effectively to treat the above described conditions and to relieve pain suffered by the patient. However, there are still disadvantages to the present fixation implants and surgical implantation techniques. The historical development of such implants is set forth in U.S. Pat. Nos. 5,505,732, 5,514,180, and 5,888,223, for example, all incorporated herein by reference.
One technique for spinal fixation includes the immobilization of the spine by the use of spine rods of many different configurations that run generally parallel to the spine. Typically, the posterior surface of the spine is isolated and bone screws are first fastened to the pedicles of the appropriate vertebrae or to the sacrum and act as anchor points for the spine rods. The bone screws are generally placed two per vertebra, one at each pedicle on either side of the spinous process. Clamp assemblies join the spine rods to the screws. The spine rods are generally bent to achieve the desired curvature of the spinal column. Wires may also be employed to stabilize rods to vertebrae. These techniques are described further in U.S. Pat. No. 5,415,661, for example, incorporated herein by reference.
These types of rod systems can be effective, but require a posterior approach and implanting screws into or clamps to each vertebra over the area to be treated. To stabilize the implanted system sufficiently, one vertebra above and one vertebra below the area to be treated are often used for implanting pedicle screws. Since the pedicles of vertebrae above the second lumbar vertebra (L2) are very small, only small bone screws can be used which sometimes do not give the needed support to stabilize the spine. These rods and screws and clamps or wires are surgically fixed to the spine from a posterior approach, and the procedure is difficult. A large bending moment is applied to such rod assemblies, and because the rods are located outside the spinal column, they depend on the holding power of the associated components which can pull out of or away from the vertebral bone.
In a variation of this technique disclosed in U.S. Pat. Nos. 4,553,273 and 4,636,217 (both described in U.S. Pat. No. 5,735,899 incorporated herein by reference, two of three vertebrae are joined by surgically obtaining access to the interior of the upper and lower vertebral bodies through excision of the middle vertebral body. In the ""899 patent, these approaches are referred to as xe2x80x9cintraosseousxe2x80x9d approaches, although they are more properly referred to as xe2x80x9cinterosseousxe2x80x9d approaches by virtue of the removal of the middle vertebral body. The removal is necessary to enable a lateral insertion of the implant into the space it occupied so that the opposite ends of the implant can be driven upward and downward into the upper and lower vertebral bodies. These approaches are criticized as failing to provide adequate medial-lateral and rotational support in the ""899 patent. In the ""889 patent, an anterior approach is made, slots are created in the upper and lower vertebrae, and rod ends are fitted into the slots and attached to the remaining vertebral bodies of the upper and lower vertebrae by laterally extending screws.
A wide variety of anterior, extraosseous fixation implants, primarily anterior plate systems, have also been proposed or surgically used. One type of anterior plate system involves a titanium plate with unicortical titanium bone screws that lock to the plate and are placed over the anterior surface of a vertebral body. Another type of anterior plate system involves the use of bicortical screws that do not lock to the plate. The bone screws have to be long enough to bite into both sides of the vertebral body to gain enough strength to obtain the needed stability. These devices are difficult to place due to the length of the screws, and damage occurs when the screws are placed improperly.
A number of disc shaped replacements or artificial disc implants and methods of insertion have been proposed as disclosed, for example, in U.S. Pat. Nos. 5,514,180 and 5,888,223, for example. A further type of disc reinforcement or augmentation implant that has been clinically employed for spinal fusion comprises a hollow cylindrical titanium cage that is externally threaded and is screwed laterally into place in a bore formed in the disc between two adjacent vertebrae. Bone grafts from cadavers or the pelvis or substances that promote bone growth are then packed into the hollow center of the cage to encourage bone growth through the cage pores to achieve fusion of the two adjacent vertebrae. Two such cage implants and the surgical tools employed to place them are disclosed in U.S. Pat. Nos. 5,505,732 and 5,700,291, for example. The cage implants and the associated surgical tools and approaches require precise drilling of a relatively large hole for each such cage laterally between two adjacent vertebral bodies and then threading a cage into each prepared hole. The large hole or holes can compromise the integrity of the vertebral bodies, and if drilled too posteriorly, can injure the spinal cord. The end plates of the vertebral bodies, which comprise very hard bone and help to give the vertebral bodies needed strength, are usually destroyed during the drilling. The cylindrical cage or cages are now harder than the remaining bone of the vertebral bodies, and the vertebral bodies tend to collapse or xe2x80x9ctelescope,xe2x80x9d together. The telescoping causes the length of the vertebral column to shorten and can cause damage to the spinal cord and nerves that pass between the two adjacent vertebrae.
Methods and apparatus for accessing the discs and vertebrae by lateral surgical approaches are described in U.S. Pat. No. 5,976,146. The intervening muscle groups or other tissues are spread apart by a cavity forming and securing tool set disclosed in the ""146 patent to enable endoscope aided, lateral access to damaged vertebrae and discs and to perform corrective surgical procedures.
R. Johnsson et al. report the results of the use of biodegradable rods to augment posterolateral fusion of L5-S1 or L4-S1 in xe2x80x9cPosterolateral lumbar fusion using facet joint fixation with biodegradeable rods: a pilot studyxe2x80x9d Eur Spine J 6:14-48xe2x80x2 (1997). In this surgical technique, the posterolateral surfaces of the lumbrosacral spine were exposed, and two canals were bored through facets of the vertebrae to be fused. A rod formed of self-reinforced polyglycolic acid composite material was inserted through each canal, and fixed by absorption of body fluids and expansion therein. While successful fusion of L5-S1 was reported in a number of cases, fusion of L4-S1 was unsuccessful or inadequate, and lateral surgical exposure and stripping of the vertebrae facets was still necessary.
A compilation of the above described surgical techniques and spinal implants and others that have been used clinically is set forth in certain chapters of the book entitled Lumbosacral and Spinopelvic Fixation, edited by Joseph Y. Margolies et al. (Lippincott-Raven Publishers, Philadelphia, 1996). Attention is directed particularly to Chapters 1, 2, 16, 18, 38, 42 and 44. In xe2x80x9cLumbopelvic Fusionxe2x80x9d (Chapter 38 by Prof. Rene P. Louis, MD) techniques for repairing a spondylolisthesis, that is a severe displacement of L5 with respect to S1 and the intervening disc, are described and depicted. An anterior lateral exposure of L5 and S1 is made, a discectomy is performed, and the orientation of L5 to S1 is mechanically corrected using a reduction tool, if the displacement is severe. A fibula graft or metal Judet screw is inserted as a dowel through a bore formed extending caudally through L5 and into S1. Further spacer implants are placed in the space occupied by the extracted disc between L5 and S1. External bridge plates or rods are also optionally installed.
The posterolateral or anterior lateral approach is necessitated to correct the severe spondylolisthesis displacement using the reduction tool and results in tissue injury. Because of this approach and need, the caudal bore and inserted the Judet screw can only traverse L5 and S1.
The above-described spinal implant approaches involve highly invasive surgery that laterally exposes the anterior or posterior portions of the vertebrae to be supported or fused. Extensive muscular stripping and bone preparation can be necessary. As a result, the spinal column can be further weakened and/or result in surgery induced pain syndromes. Thus, presently used surgical fixation and fusion techniques involving the lower lumbar vertebrae suffer from numerous disadvantages. It is preferable to avoid the lateral exposure to correct less severe spondylolisthesis and other spinal injuries or defects affecting the lumbar and sacral vertebrae and discs.
A wide variety of orthopedic implants have also been proposed or clinically employed to stabilize broken bones or secure artificial hip, knee and finger joints. Frequently, rods or joint supports are placed longitudinally within longitudinal bores made in elongated bones, e.g., the femur. A surgical method is disclosed in U.S. Pat. No. 5,514,137 for stabilizing a broken femur or other long bones using an elongated rod and resorbable cement. To accomplish a placement of a rod into any single bone, an end of a bone is exposed and a channel is drilled from the exposed end to the other end. Thereafter, a hollow rod is inserted, and resorbable cement is injected through the hollow rod, so as to provide fixation between the distal end of the rod and the cancellous tissue that surrounds the rod. A cement introducer device can also be used for the injection of cement. A brief reference is made in the ""137 patent to the possibility of placing rods in or adjacent to the spine in the same manner, but no particular approach or devices are described.
The present invention has at least one objective of providing a practical and advantageous system, method and tools for accessing the spinal vertebrae to repair or augment damaged vertebrae and discs or to insert spinal implants in various manners that overcome the above described disadvantages of posterior and anterior lateral approaches thereto and minimize surgical trauma to the patient.
The methods and surgical instrumentation of the present invention provide posterior and anterior trans-sacral access to a series of adjacent vertebrae located within a human lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs. A number of related trans-sacral axial spinal instrumentation/fusion (TASIF) methods and surgical tool sets are provided by various alternative embodiments of the present invention. Certain of the tools are selectively employed to form a percutaneous (i.e., through the skin) pathway from an anterior or posterior skin incision to a respective anterior or posterior position, e.g., a target point of a sacral surface or the cephalad end of a pilot hole bored through the sacrum and one or more lumbar vertebrae. The percutaneous pathway is generally axially aligned with an anterior axial instrumentation/fusion line (AAIFL) or a posterior axial instrumentation/fusion line (PAIFL) extending from the respective anterior or posterior target point through at least one sacral vertebral body and one or more lumbar vertebral body in the cephalad direction and visualized by radiographic or fluoroscopic equipment. The AAIFL and PAIFL follow the curvature of the vertebral bodies, although the AAIFL can be straight or relatively straight, depending on the number of vertebrae that the AAIFL is extended through.
The anterior or posterior percutaneous pathway so formed enables introduction of further tools and instruments for forming an anterior or posterior percutaneous tract extending from the skin incision to the respective anterior or posterior target point of the sacral surface or, in some embodiments, the cephalad end of a pilot hole over which or through which further instruments are introduced. The xe2x80x9canterior, presacral, percutaneous tractxe2x80x9d disclosed herein extends through the xe2x80x9cpresacral spacexe2x80x9d anterior to the sacrum.
The anterior or posterior percutaneous tract is preferably used to bore one or more respective anterior or posterior TASIF bore in the cephalad direction through one or more lumbar vertebral bodies and intervening discs, if present. A single anterior or posterior TASIF bore is preferably aligned axially with the respective visualized AAIFL or PAIFL, and plural anterior or posterior TASIF bores are preferably aligned in parallel with the respective visualized AAIFL or PAIFL. Introduction of spinal implants and instruments for performing discectomies and/or disc and/or vertebral body augmentation is enabled by the provision of the percutaneous pathway in accordance with the present invention and formation of the anterior or posterior TASIF bore(s).
The posterior percutaneous tract preferably extends from a posterior skin incision into the posterior sacrum to a posterior target point exposed by a laminectomy. This posterior percutaneous tract has a tract axis aligned with the visualized PAIFL to provide working space, exposure of the sacrum, and alignment of the boring tool with the visualized PAIFL. The posterior percutaneous tract can take the form of a lumen of a tract sheath introduced through the percutaneous pathway or a guidewire whereby the guidewire provides a percutaneous tract for over the wire passage extending from the skin incision to the posterior target point and aligned with the visualized PAIFL. Either or both of the tract sheath or guidewire can comprise distal fixation mechanisms that enable fixation to the sacral vertebral surface at the posterior target point for through the sheath or over the wire introduction of boring tools or other instruments. Prior to boring the posterior TASIF bore(s), a pilot hole for each such posterior TASIF bore is optionally bored along or parallel with the visualized PAIFL, and the guidewire distal end is affixed to vertebral bone at the cephalad end of the pilot hole to provide the percutaneous tract for guiding a drill or other instrument to form the posterior TASIF bore or conduct discectomies or disc or vertebral bone augmentation.
Certain of the surgical tools take the form of elongated solid body members extending from proximal to distal ends thereof. Such solid body members may be used in combination with or sequentially with elongated hollow body members. Certain of these solid body and hollow body members can have distal fixation mechanisms for attachment to bone and/or can be angles to be aligned with and bear against sacral bone.
The anterior percutaneous pathway is preferably accomplished employing an elongated guide member that is introduced through the skin incision and advanced against the anterior sacrum through the presacral space until the guide member distal end is located at the anterior target point. The posterior viscera are pushed aside as the guide member is advanced through presacral space and axially aligned with the AAIFL at the anterior target point of the anterior sacral surface.
The guide member may take a variety of forms including a blunt tip rod or a guide assembly of an inner occluder and an outer tubular member fitted together having a tubular member lumen receiving the occluder. The occluder may take the form of a solid body member, e.g., an obdurator, a stylet, a guidewire or the like, and the tubular member may take the form of a needle, a trocar, a catheter or the like. Either or both of the inner occluder and outer tubular member may comprise distal fixation mechanisms that enable fixation to the sacral vertebral surface at the anterior target point and/or at the cephalad end of a pilot hole for each such anterior TASIF bore optionally bored along or parallel with the visualized AAIFL. The occluder can be employed to blunt the tip of the outer tubular member during introduction to the anterior target point, if the outer tubular member comprises a distal tip fixation mechanism that would otherwise prematurely engage the sacral bone. Or the occluder can have a distal tip fixation mechanism and be retracted within the outer tubular member to prevent its premature attachment to sacral bone during introduction to the anterior target point.
In its simplest forms, the anterior, presacral, percutaneous tract can take the form of the lumen of the outer tubular member upon removal of the occluder. The anterior percutaneous pathway can be expanded to form the anterior, presacral, percutaneous tract through the patient""s anterior presacral space having a tract axis aligned with the visualized AAIFL to provide working space and exposure of the sacrum. In one embodiment, a guidewire having a distal fixation mechanism (which may comprise the occluder) provides the anterior, presacral, percutaneous tract for over-the-wire passage extending from the skin incision to the target point and aligned with the visualized AAIFL. In further embodiments, the lumen of a further tract sheath introduced through the percutaneous pathway, e.g., over the guidewire or after removal of the guidewire, provides a percutaneous tract for over the wire passage extending from the skin incision to the target point and aligned with the visualized AAIFL. The further tract sheath preferably has a distal tract sheath fixation mechanism and configuration that enables alignment and attachment to the anterior sacral bone at the anterior target point to maintain the tract sheath lumen aligned axially with a the visualized AAIFL.
The tissue surrounding the skin incision and the anterior, presacral, percutaneous pathway through the presacral space may optionally be dilated to form an enlarged diameter presacral, percutaneous tract surrounding a guidewire or tubular member and/or to accommodate the insertion of a tract sheath over the guidewire. Dilation can be accomplished manually or by use of one or more dilator or dilatation balloon catheter or any tubular device fitted over a previously extended tubular member or guidewire.
Additionally, a pilot hole can be bored in axial alignment or parallel with the visualized AAIFL by a boring tool introduced through the outer tubular member lumen for each such anterior TASIF bore bored along or parallel with the visualized AAIFL. The guidewire distal end fixation mechanism is then affixed to vertebral bone at the cephalad end of the pilot hole to provide the percutaneous tract for guiding a drill or other instrument to form the anterior TASIF bore or conduct discectomies or disc or vertebral bone augmentation.
In particular embodiments of the present invention, in the anterior TASIF approach, the junction of S1 and S2 is located through a presacral, percutaneous tract posterior to the rectum and extending from a skin incision adjacent the coccyx. A relatively straight anterior TASIF axial bore into at least L5 can be formed in the vertebral column accessed via the anterior, presacral, percutaneous tract to receive a TASIF implant or interventional tools inserted through the anterior, presacral, percutaneous tract. However, the anterior TASIF axial bore can also be curved to follow the curvature of the vertebrae L4, L3, et seq. in the cephalad direction following a visualized, curved, AAIFL extending therethrough.
In a preferred posterior TASIF approach, the posterior sacrum is exposed, a laminectomy is performed at S2, and the posterior percutaneous tract is formed using one of the above-summarized procedures and percutaneous tract tool sets. A curved axial bore is then made upwardly through S2, S1 and into at least L5 and optionally extended and curved to follow the curvature of the vertebrae L4, L3, et seq. in the cephalad direction. A curved TASIF implant or rod can be inserted into the TASIF axial bore to bridge the vertebrae and the intervening discs, if present.
Thus, the various embodiments of the present invention provide access to anterior and posterior target points of the anterior or posterior sacrum preparatory to forming anterior or posterior TASIF bores that extend in the cephalad direction and can be employed to introduce instruments for treatment of vertebral bodies, intervertebral discs and introduction of axially aligned spinal implants as described in further detail in the above-referenced provisional application No. 60/182,748. In either the posterior or anterior approach, multiple bores may be made side-by-side to receive multiple spinal implants.
The access procedures for forming the anterior or posterior percutaneous tract and the subsequently conducted surgical repair and/or implantation procedures are minimally invasive and requires a short, if any, post-implantation hospitalization and recovery period and reduced discomfort to the patient. The access procedures avoid the muscle stripping required to access the vertebrae and/or discs or removal of strong anterior vertebral body bone and intervening discs attendant to the conventional lateral surgical approaches described above
The anterior and posterior TASIF approaches also allow disc surgery or disc augmentation through the TASIF bore or pilot hole of all discs traversed by the TASIF axial bore or pilot hole in a minimally invasive manner. Moreover, these approaches can be employed a minimally invasive manner to perform vertebroblasty of the vertebrae traversed by the TASIF axial bore or pilot hole to augment the vertebral bone in cases of compression fracture of the vertebral bone. Vertebroblasty is procedure for augmentation of collapsed vertebral bodies by pumped in materials, e.g., bone cement. In the past, it has been accomplished through a lateral approach of a needle into a single vertebral body and pumping the cement through the needle lumen. The present invention allows larger diameter access to multiple vertebral bodies through the axial approach.
The present invention further enables use of a number of differing types of TASIF implants or rods that can be inserted into the TASIF axial bore or bores. Such implantable vertebral prostheses align, strengthen, and fuse the adjacent vertebrae particularly in the lumbar region of the spinal column. The elongated, axially extending TASIF implants or rods implanted using the percutaneous tracts formed in accordance with the present invention reinforce the relatively strong anterior vertebral bodies and should prevent potentially damaging telescoping of adjacent vertebrae.
The TASIF spinal implants or rods can be implanted in accordance with the present invention in a less traumatic manner than conventional lateral exposure and placement of conventional vertebral prostheses, and the need to implant screws or extend wires laterally through the vertebral bodies and a rod or rods is eliminated. Unlike conventional spinal rods, the TASIF implants or rods that can be implanted inherently possess a low profile and would usually not be felt by the patient after healing.
Moreover, it is contemplated that the anterior or posterior TASIF pilot hole or axial bore may also be used to receive pain relief stimulation electrodes coupled through leads to implantable pulse generators for providing electrical stimulation of the bone and adjoining nerves for pain relief and/or to stimulate bone growth. Other therapeutic spinal implants can be implanted therein to elute drugs or analgesics or emit radiation for treatment of various diseases or pain syndromes.